The invention relates to a method for allocating downlink electromagnetic power to enhance performance of a wireless network.
Whenever a wireless network is initially installed or expanded, various wireless parameters must be tuned to proper values prior to full commercial operation. The tuning of wireless parameters is referred to as radio frequency (RF)network optimization. The RF optimization includes adjusting the downlink transmit power of base stations.
Wireless service providers often have relied upon a trial-and-error strategy to optimize radio frequency antenna coverage of cells or other geographic areas within a wireless network. The trial-and-error strategy requires repeated measurements at the same locations through iterative test drives until a feasible downlink transmit power for each base station is found. The test drive refers to taking radio frequency measurement samples from a vehicle which is equipped to measure radio frequency parameters versus location while driving through the coverage area of a wireless network. Based on recorded measurements of parameters in a cluster of cells during a test drive, recommendations on adjusting system parameters are established. However, the trial-and-error approach sometimes leads to quality deterioration or service interruption if incorrect recommendations are applied to an operational system. After the recommended changes to system parameters are implemented, another test drive typically is completed to validate system performance. If the latest test drive did not indicate adequate performance, the wireless network or expansion may be delayed from commercial operation, while yet another round of parameter adjustments is followed by a corresponding test drive.
Even if a wireless network timely goes into commercial operation, improper radio frequency optimization may reduce the capacity of a wireless network. Failure to accurately set the parameters of downlink transmit power may lead to unnecessary expenditures for capital intensive cellular infrastructure. For example, additional channel capacity or additional cell sites, which are not truly needed, may be added to compensate for an incorrectly optimized wireless system.
The trial-and-error approach to optimization wastes valuable time of engineering and technical resources by often entailing iterative or multiple field measurements to obtain an acceptable solution for radio frequency optimization. The repetitive nature of the trial-and-error tends to make such an approach difficult or impractical for handling large networks. Thus, a need exists for improving the accuracy of optimization rather than relying on the time-consuming and happenstance accumulation of empirical data.
During radio frequency optimization, the overall geographic coverage area may be divided into clusters of smaller geometric regions, each encompassing a few adjacent cells. The trial-and-error approach is then applied to the clusters, one after another. After finishing all clusters, the wireless network is re-optimized as a whole, particularly at the boundary between clusters, with the same trial-and-error method. Thus, the trial-and-error approach is time consuming and may not even produce suitable or optimum coverage results.
In accordance with the invention, a method for allocating downlink transmit-power in a wireless network determines downlink transmit powers to permit a target performance goal to be satisfied for defined radio frequency coverage areas. Base stations transmit electromagnetic transmissions. Received signal parameters of the electromagnetic transmissions are measured at measurement locations within defined radio frequency coverage areas. A data processing system determines propagation factors associated with the electromagnetic transmissions as a function of the measurement locations. A data processing system determines a downlink transmit power for at least one of the base stations based upon at least one target performance goal for the coverage areas and the propagation factors.
The target performance goal may comprise a target carrier-to-interference ratio for the coverage areas with reference to the propagation factor associated with each of the measurement locations. The processing system may calibrate the downlink transmit power to satisfy the target carrier-to-interference ratio for the measurement locations with a defined reliability. For example, the downlink transmit power may be selected such that a corresponding actual carrier-to-interference ratio meets or minimally exceeds the target-to-carrier interference ratio for the measurement locations with a defined reliability. The defined reliability may be defined in terms of probability or other statistical measures.
The systematic attributes of the method and its associated data structure increase the efficiency of radio frequency optimization by eliminating the recursive or iterative nature of taking field measurements pursuant to the conventional trial-and-error approach. Moreover, the method of the invention is well-suited for reliable execution on a general purpose computer.